13A-27
MPI – TROUBLESHOOTING
<Examples of abnormal waveforms>
• Example 1
Waveform characteristics
A rectangular waveform is produced even though the
engine has not been started.
Cause of the problem
Sensor interface fault
• Example 2
Waveform characteristics
The waveform is displaced to the left or the right.
Cause of the problem
The timing belt is loose.
There is an abnormality in the sensor disc.
8-2 Intake cam position sensor
<Measurement method>
(1) Disconnect the intake cam position sensor connector and
connect the special test harness (MB991709) in its place.
(All terminals should be connected).
(2) Connect the oscilloscope probe to the No.2 terminal of the
intake cam position sensor connector.
Note
When measuring at the engine ECU connector, connect the
No.53 terminal (intake cam position sensor) to the
oscilloscope probe.
(3) When checking the output signal of the intake cam position
sensor, observe the output signal of the crank angle sensor
at the same time.
crank
angle
sensor
connector
intake cam position
sensor connector
oscilloscope
<Standard waveforms>
Observation conditions
Intake cam position sensor Crank angle sensor
Probe switch X1 x1
AC-GND-DC DC DC
TIME/DIV. 10ms 10 ms
VOLTS/DIV. 2V 2V
Other - -
Engine Idling
